Devices of the type and for the purpose indicated hereabove are already known. These prior art devices comprise means for preparation of the fibers and means for dosing the material for the formation of small mattresses of cotton, rayon, synthetic fiber, etc. These known devices however are not free from serious inconveniences and drawbacks, especially with respect to the uniformity of distribution of the material in the formation of the wads and in the possibility of a careful and minute control of the wad and of the recycling of the excess material which is not accepted by the carding machine.